1. Field of the Invention.
The present invention relates to an image pickup lens unit. More particularly, the invention relates to an image pickup lens unit for use with a small-sized CCD or CMOS, which serves as an image pickup element, and which enables an image pickup lens to be united with a holder without being incorporated into a barrel.
2. Description of the Related Art
Conventionally, as shown in FIG. 6, an image pickup lens unit for use with a CCD or CMOS is composed of at least five components; namely, a lens barrel, a lens retainer, an image pickup lens, a stop, :and a holder. However, it has been possible to freely perform focus adjustment of the image pickup lens after assembly thereof.
In recent years, there has been a demand for very significant reductions in both the size and cost of electronic camera equipment. In this environment, the image pickup lens unit for cameras are required to reduce the number of components, size,. and cost. Particularly, there has been a movement to unify the holder and the lens in the monitor lens unit used in mobile equipment or cellular phones in order to accommodate the trend towards reductions in the size and cost of such equipment.
In order to meet the above requirement, an united-type image pickup lens unit has been devised in which a lens is fitted into a holder, for use in electronic camera equipment employing a solid image pickup element. The image pickup lens unit is composed of three components; namely, a retainer having an aperture stop, an image pickup lens, and a holder. Alternatively, the lens surface is subjected to printing so as to form an aperture stop, instead of using a retainer having an aperture stop. Therefore, the image pickup lens unit is composed of two components; namely, an image pickup lens and a holder, thereby-realizing low cost through simplified assembly and a reduction in the number of components. Since the number of components is small, such an image pickup lens unit can be easily assembled and is therefore suitable for mass production.
However, since the above image pickup lens unit employing a united lens-and-holder structure does not have a focusing mechanism after assembly, maintaining high standards of manufacturing accuracy of respective components and the attachment accuracy of a CCD or CMOS are very important in terms of image quality. Specifically, the shorter the focal distance of the image pickup lens unit, the more important the distance of the image pickup lens and an image plane, as of a CCD or CMOS, becomes in terms of image quality. Since an image pickup lens for use with the above-mentioned image pickup element employs high-brightness; specifically Fno=2.0-2.8, the focal depth becomes shallow. As a result, even a minor error in lens position causes defocus. In other words, since manufacturing errors of the respective components cause a variation in the design distance to an object, defocus will occur even when the distance to an object is set to the design distance in the course of mass production, resulting in poor image quality or an unfocused image.
Furthermore, an machining error of an image pickup lens, a contraction error of an image pickup lens in the course of molding, or a holder dimensional error, for example, will cause a defect in the final image. Accordingly, even when the united lens-and-holder structure is employed in an attempt to reduce cost and weight and in an attempt to facilitate mass production, defects will frequently result unless a focusing mechanism is employed, so that the costs increase undesirably, and mass production becomes difficult.
In view of growing demands for inexpensive high-performance lenses so as to be compatible with electronic image pickup equipment which is undergoing reduction in size and weight, an object of the present invention is to provide a small-sized, inexpensive, high-performance image pickup lens unit.
More particularly, an object of the present invention is to provide a high-performance image pickup lens unit for use with electronic image pickup equipment, enabling an image pickup lens and a holder to be united with each other through, for example, fitting, so as to avoid use of a barrelxe2x80x94which is conventionally used to hold and adjust the lensxe2x80x94for reduction in weight and costs, and enabling focusing after assembly.
Herein, an assembly obtained through incorporation of an image pickup lens into a peripheral component (a holder, for example) is called an xe2x80x9cimage pickup lens unit.xe2x80x9d
A first aspect of the present invention provides an image pickup lens unit comprising, as viewed from an object side, a retainer having an aperture stop, an image pickup lens, and a holder. The retainer and the image pickup lens are united with each other. The holder assumes a substantially cylindrical shape and accommodates the image pickup lens such that the image pickup lens is united with the holder in a manner movable in relation to the holder, whereby movement of the retainer causes the image pickup lens to move in relation to the holder to thereby carry out focus adjustment.
According to the first aspect, movement of the retainer having an aperture stop causes the image pickup lens to move, since the image pickup lens is united with the retainer. The image pickup lens moves while being accommodated within the holder, thereby maintaining a state in which the image pickup lens is united with the holder. Through movement of the image pickup lens, the image pickup lens is focused.
A second aspect of the present invention provides an image pickup lens unit comprising, as viewed from an object side, a retainer having an aperture stop and assuming a circular cross section, an image pickup lens assuming a circular cross section, and a holder assuming a circular cross section. The retainer and the image pickup, lens are united with each other. At least one protrusion is formed on a circumferential portion of the image pickup lens. The holder assumes a substantially cylindrical shape and has an elongated groove formed on an inner cylindrical wall thereof in such a manner that the groove extends in the circumferential direction and inclines in the axial direction. The holder accommodates the image pickup lens such that the protrusion is fitted into the elongated groove to thereby unite the image pickup lens with the holder in a manner movable along the elongated groove in relation to the holder, whereby rotation of the retainer causes the image pickup lens to move along the elongated groove in relation to the holder, thereby moving the image pickup lens axially so as to carry out focus adjustment.
According to the second aspect, when the retainer having an aperture stop is rotated, the image pickup lens rotates and moves, since the image pickup lens is united with the retainer. The protrusion formed on the circumferential portion of the image pickup lens is fitted into the elongated groove, which is formed on the inner cylindrical wall of the holder. Accordingly, as the image pickup lens rotates, the protrusion moves along the elongated groove, which inclines in the axial direction of the holder; as a result, the image pickup lens moves axially. The image pickup lens moves rotatively while being accommodated within the holder, thereby maintaining a state in which the image pickup lens is united with the holder. Through axial movement of the image pickup lens, the image pickup lens is focused.
A third aspect of the present invention provides an image pickup lens unit comprising, as viewed from an object side, an image pickup lens assuming a circular cross section; and a holder assuming a circular cross section. The surface of the image pickup lens which faces an object, the surface of the image pickup lens which faces an image plane, or both of the surfaces are subjected to printing at a peripheral portion(s) thereof so as to form an aperture stop. At least one protrusion is formed on a circumferential portion of the image pickup lens. The holder assumes a substantially cylindrical shape and has an elongated groove formed on an inner cylindrical wall thereof in such a manner that the groove extends in the circumferential direction and inclines in the axial direction. The holder accommodates the image pickup lens such that the protrusion is fitted into the elongated groove to thereby unite the image pickup lens with the holder in a manner movable along the elongated groove in relation to the holder, whereby rotation of the image pickup lens causes the image pickup lens to move along the elongated groove in relation to the holder, thereby moving the image pickup lens axially so as to carry out focus adjustment.
According to the third aspect, the protrusion formed on the circumferential portion of the image pickup lens is fitted into the elongated groove, which is formed on the inner cylindrical wall of the holder. Accordingly, as the image pickup lens rotates, the protrusion moves along the elongated groove, which inclines in the axial direction of the holder; as a result, the image pickup lens moves axially. The image pickup lens moves rotatively while being accommodated within the holder, thereby maintaining a state in which the image pickup lens is united with the holder. Through axial movement of the image pickup lens, the image pickup lens is focused.
A fourth aspect of the present invention provides an image pickup lens unit comprising, as viewed from an object side, a retainer having an aperture stop and assuming a circular cross section, an image pickup lens assuming a circular cross section, and a holder assuming a circular cross section. The retainer and the image pickup lens are united with each other. At least one protrusion is formed on a circumferential portion of the retainer. The holder assumes a substantially cylindrical shape and has an elongated groove formed on an inner cylindrical wall thereof in such a manner that the groove extends in the circumferential direction and inclines in the axial direction. The holder accommodates the image pickup lens such that the protrusion is fitted into the elongated groove to thereby unite the retainer with the holder in a manner movable along the elongated groove in relation to the holder, whereby rotation of the retainer causes the image pickup lens to move along the elongated groove in relation to the holder, thereby moving the image pickup lens axially so as to carry out focus adjustment.
According to the fourth aspect, when the retainer having an aperture stop is. rotated, the image pickup lens rotates and moves, since the image pickup lens is united with the retainer. The protrusion formed on the circumferential portion of the retainer is fitted into the elongated groove, which is formed on the inner cylindrical wall of the holder. Accordingly, as the retainer rotates, the protrusion moves along the elongated groove, which inclines in. the axial direction of the holder; as a result, the retainer moves axially, and thus the image pickup lens moves axially. The image pickup lens moves rotatively while being accommodated within the holder, thereby maintaining a state in which the image pickup lens is united with the holder. Through axial movement of the image pickup lens, the image pickup lens is focused.
A fifth aspect of the present invention provides an image pickup lens unit comprising, as viewed from an object side, a retainer having an aperture stop and assuming a circular cross section, an image pickup lens assuming a circular cross section, and a holder assuming a circular cross section. The retainer and the image pickup lens are united with each other. At least two toothlets are formed on a peripheral portion of a surface of the image pickup lens which faces an image plane, such that upper faces thereof have sloped surfaces formed along the circumference of the image pickup lens. The holder assumes a substantially cylindrical shape and has at least two protrusions formed on an inner cylindrical wall thereof so as to hold the image pickup lens through contact between the protrusions and the upper faces of the toothlets. The holder accommodates the image pickup lens such that the image pickup lens can move in relation to the holder while contact between the protrusions and the sloped surfaces of the upper faces of the toothlets is maintained, whereby rotation of the retainer causes the image pickup lens to move while maintaining contact of the sloped surfaces with the protrusions, thereby moving the image pickup lens axially so as to carry out focus adjustment.
According to the fifth aspect, when the retainer having an aperture stop is rotated, the image pickup lens rotates and moves, since the image pickup lens is united with the retainer. The image pickup lens is held within the holder such that the upper faces of the toothlets, which are formed on a peripheral portion of the surface of the image pickup lens which faces an image plane, are in contact with the protrusions formed on the inner cylindrical wall of the holder. Rotation of the retainer causes the image pickup lens to move rotatively while contact between the protrusions and the sloped surfaces of the upper faces is maintained. Since the upper faces of the toothlets have sloped surfaces sloping along the circumference direction, the image pickup lens rotates while maintaining contact between the protrusions and the upper faces of the toothlets. Therefore, the image pickup lens rotates in accordance with the shape of the sloped surfaces of the upper faces of the toothlets; as a result, the image pickup lens moves axially. The image pickup lens moves rotatively while being accommodated within the holder, thereby maintaining a state in which the image pickup lens is united with the holder. Through axial movement of the image pickup lens, the image pickup lens can be focused.
According to the first aspect, in spite of employment of the unitary lens-and-holder structure, the image pickup lens can be focused through movement thereof. Thus, even when errors in manufacture of components or errors in attachment of a CCD or CMOS are of a large magnitude, the image pickup lens can be focused accordingly after assembly. Therefore, a small-sized, high-performance image pickup lens unit can be obtained. Furthermore, simplified assembly and a reduction in the number of components bring about a reduction in weight and cost and enhance suitability to mass production. Also, accuracy required of components is not very high, thereby reducing the cost of the components. By virtue of a synergetic effect of these affirmative factors, costs are reduced further. Additionally, macrophotographic adjustment is possible, thereby enhancing convenience.
According to the second aspect, in spite of employment of the unitary lens-and-holder structure, the image pickup lens can be readily focused after assembly through rotation of the retainer having an aperture stop. Thus, a high-performance image pickup lens unit can be obtained. Simplified assembly and a reduction in the number of components bring about a reduction in weight and cost and enhance suitability to mass production. Also, accuracy required of components is not very high, thereby reducing the cost of the components. By virtue of a synergetic effect of these affirmative factors, costs are reduced further.
According to the third aspect, in spite of employment of the unitary lens-and-holder structure, the image pickup lens can be readily focused after assembly through rotation thereof. Thus, a high-performance image pickup lens unit can be obtained. Since the retainer having an aperture stop is not employed, the number of components is reduced accordingly. Simplified assembly and a reduction in the number of components bring about a reduction in weight and cost and enhance suitability to mass production. Also, accuracy required of components is not very high, thereby reducing the cost of the components. By virtue of a synergetic effect of these affirmative factors, costs are reduced further.
According to the fourth aspect, in spite of employment of the unitary lens-and-holder structure, the image pickup lens can be readily focused after assembly through rotation of the retainer having an aperture stop. Thus, a high-performance image pickup lens unit can be obtained. Simplified assembly and a reduction in the number of components bring about a reduction in weight and cost and enhance suitability to mass production. Also, accuracy required of components is not very high, thereby reducing the cost of the components. By virtue of a synergetic effect of these affirmative factors, costs are reduced further. Additionally, the manufacture of the image pickup lens does not involve formation of the protrusion, thereby providing another affirmative factor for further reduction in cost.
According to the fifth aspect, in spite of employment of the unitary lens-and-holder structure, the image pickup lens can be readily focused after assembly through rotation of the retainer having an aperture stop. Thus, a high-performance image pickup lens unit can be obtained. Simplified assembly and a reduction in the number of components bring about a reduction in weight and cost and enhance suitability to mass production. Also, accuracy required of components is not very high, thereby reducing the cost of the components. By virtue of a synergetic effect of these affirmative factors, costs are reduced further.